1. Field of the Invention
The present invention relates to a fuel cell system including a fuel cell stack formed by stacking a plurality of power generation cells, and a humidifier for humidifying at least one of reactant gases supplied to the fuel cell stack using humidified fluid.
2. Description of the Related Art
For example, a polymer electrolyte fuel cell employs an electrolyte membrane (electrolyte) comprising a polymer ion exchange membrane. The electrolyte membrane is interposed between an anode and a cathode to form a membrane electrode assembly (electrolyte electrode assembly). The membrane electrode assembly is sandwiched between separators to form a power generation cell. In use, normally, a predetermined number of power generation cells are stacked together to form a fuel cell stack.
In the fuel cell, in order to achieve the desired ion conductivity, it is necessary to maintain the desired humidified state of the electrolyte membrane. For this purpose, in general, the oxygen-containing gas and the fuel gas are humidified through a humidifier before these gases are supplied to the fuel cell.
For example, a fuel cell humidification system disclosed in Japanese Laid-Open patent publication No. 2001-216983 includes a stack 1 and a humidification unit 2 as shown in FIG. 8. A connection surface 1a of the stack 1 and a connection surface 2a of the humidification unit 2 are overlapped with each other to connect the stack 1 and the humidification unit 2 together into one piece.
A fuel gas inlet port 3a and a fuel gas outlet port 3b are formed at positions along one diagonal line on the connection surface 1a of the stack 1, and a supply gas inlet port 4a and a supply gas outlet port 4b are provided at positions along the other diagonal line on the connection surface 1a. Further, a coolant water inlet port 5a and a coolant water outlet port 5b are formed at substantially central positions on the left and right sides.
On the connection surface 2a of the humidification unit 2, in correspondence with the ports of the stack 1, a fuel gas discharge port 3c, a fuel gas intake port 3d, a supply gas discharge port 4c, an off gas intake port 4d, a coolant water discharge port 5c, and a coolant water intake port 5d are formed.
As described above, the humidification unit 2 and the stack 1 are combined together into one piece. Therefore, it is possible to easily simplify the structure and reduce the overall size and weight of the apparatus.
However, in the fuel cell humidification system, at the time of overlapping and connecting the connection surface 1a of the stack 1 and the connection surface 2a of the humidification unit 2, the pipes of the stack 1 and the pipes of the humidification unit 2 need to be accurately positioned in alignment with each other.
For example, by accurately positioning the fuel gas inlet port 3a of the stack 1 and the fuel gas discharge port 3c of the humidification unit 2 coaxially, the smooth flow of the fuel gas is achieved.